If nanometer-sized particles constitute a substance, various physical properties such as mechanical, optical, electric, and magnetic properties may be improved as compared to a conventional substance. Additionally, a novel substance containing various types of nanoparticles may be created. Many studies have been performed in the preparation of nanosubstances, in order to produce nanoceramics, nanometal, and nanocomposites containing highly pure particles having the size in the range of 1 to 100 nm, at home and abroad. When highly pure and concentrated particles having a predetermined nanometer size are formed and then attached to a substrate or subjected to reaction sintering to produce a final substance, it is the core technology to control the particle having nonometer size—to control generation, growth, movement, and attachment of the particles. However, the current technology is not satisfactory. Thus, there is a need to avoid the above-mentioned problems.
In recent years, various types of processes of forming nanoparticles have been suggested, and a process of forming and growing nanoparticles on a substrate and a process of forming a multilayered thin film after nanoparticles are formed on a substrate or an insulator thin film or only in a specific region of the substrate have been used according to the position of produced particles. In this connection, various types of processes have been developed in order to form embedded quantum particles on a thin film or a substrate. With respect to known production processes, an effort has been made to obtain a desirable particle size and distribution state and minimize agglomeration by using a conventional sputter, evaporation deposition process, CVD process, and epitaxial process, and the known production processes have been improved to avoid the problems occurring during the processes (Korean Patent Application No. 2000-0072958, Composite Polymers Containing Nanometer-sized Metal Particles and Fabrication Method Thereof, Researcher in Korea Institute of Science and Technology). In addition, a gas-phase synthesis process using inert gas condensation using heat evaporation (Making particles of uniform size, Dobson et al., U.S. Pat. No. 5,906,670) caused by gasification of a precursor, microwave plasma, and laser ablation, and a chemical gas-phase condensation process in which a metal organic substance is decomposed or synthesized by using a combustion flame or a hot-wall reactor are extensively known. Furthermore, a typical air sol spraying process is applied to produce a material that contains metal/alloy, ceramic nanopowder, a coating or doping type nanocomposite powder, or nanoparticles which are directly sprayed on a substrate in a large amount and has a narrow density distribution at normal pressure or at a low vacuum pressure. However, this is disadvantageous in that it is difficult to precisely control a distribution state of particles and the thickness of the film formed by using the spraying. In respects to a process using an aqueous solution, there is a chemical method where agglomeration between fluorescent particles is prevented, a precursor is produced, and assembling and growing are performed by using nucleus growth (Method for producing semiconductor particles, Harry R. Clark, Jr., U.S. Pat. No. 5,690,807). The chemical method includes mixing an aqueous solution of a fluorescent raw material and an aqueous solution of a compound containing light-emitting metal in a solvent, precipitating the mixture, reacting the resulting mixture and a gas-phase fluorescent raw material by using heat treatment to produce fluorescent nanoparticles having light-emitting cores, and attaching the nanoparticles to a substrate. Currently, various types of methods are suggested (Method for ion implantation induced embedded particle formation via reduction, Hampikian et al., U.S. Pat. No. 6,294,223 B1). For example, an ion implantation process is applied to control an accelerating voltage and a temperature of a substrate, so that required metal particles are formed on the substrate and a particle size distribution thereof is precisely controlled. However, the known technologies are disadvantageous because of an increase in volume caused by agglomeration, sintering, and heat treatment of the nanoparticles during the production of the nanoparticles, the necessity for various types of catalysts and additives and the undesirable yield of produced particles. Further they require a complicated production process, a long time, and high cost for the manufacturing.
The gist of the above-mentioned conventional processes of forming nanoparticles and application thereof will be given below.
(i) In the conventional process of forming nanoparticles by using a CVD process, a PVD process, and a gas-phase evaporation process, nanoparticles are formed by using improved physical and chemical deposition processes, and the production of the nanoparticles is performed by using a conventional vacuum system. However, during the process, it is impossible to deposit a plurality of components due to limitations in respects to a reaction gas, and there is a high possibility of health issues to workers during the process.
(ii) In the process of forming the nanoparticles on the substrate in a reaction gas phase by using a liquid spraying process, polymer/metal nanoparticles may be formed on the substrate or sprayed on the substrate so that highly pure nanoparticles having low density and narrow distribution are formed, or polymer/metal nanoparticles having a size of 10 nm or less may be formed. However, it leaves a problem of overcoming the nonuniform distribution at the sprayed substrate.
(iii) The process of forming the particles having a nano size on the substrate after synthesis on the aqueous solution is a representative process using a bottom-up access process. In the process, a precursor is generated in an aqueous solution and is subjected to reaction assembling, and highly pure and ultrafine particles are formed by using particle assembling. However, it is necessary to avoid agglomeration of the produced ultrafine particles.
(iv) In the process of distributing the nanoparticles on the substrate by using the ion implantation process, the particles having a nano size are formed on the substrate by using a conventional ion implantation process. It is possible to obtain a precise profile of nanoparticles by using advantages of the ion implantation and it is possible to form nanoparticles having an ion-size region. However, there is a disadvantage in that equipment used during the process is costly.
In order to avoid the above-mentioned problems of the processes, a method of producing nanoparticles from ions of metal dissolved in an acidic insulator precursor by using thermal curing is suggested (Korean Patent No. 0488896, Method of forming quantum dots using a metal thin film). The above-mentioned patent discloses a method of producing nanoparticles which includes precipitating the nanoparticles in a polyimide thin film by using imidization due to thermal curing of polyamic acid containing metal dissolved therein. According to the method which is disclosed in the above-mentioned patent, the nanoparticles having the same size may be formed in a large area in the insulator precursor by using a simple process so as to reduce agglomeration. However, since the thermal curing includes increasing the temperature from 300 to 500° C., there are problems in that ambient devices may deteriorate during thermal curing, cost is increased, and agglomeration may occur between the particles activated at high temperatures.
With respect to chemical curing, U.S. Patent Application Publication No. 2005-0100719 (published on May 12, 2005, Multilayer substrates having at least two dissimilar polyimide layers, useful for electronics-type applications, and compositions relating thereto; Kanakarajan, Kuppsuamy, et al.) discloses a method of curing a plurality of polyamic acid layers having different glass transition temperatures (Tg) in the chip package field. There, chemical curing is performed to cure the polyamic acid. However, the curing process which is disclosed in the above-mentioned patent is performed at a high temperature of 150° C. or more, and the patent does not disclose the method of forming the nanoparticles by using the curing process.